The acyl derivative of O,S-dimethyl phosphoroamidothioate is known as Orthene. Orthene is typically produced by reacting O,S-dimethyl phosphoroamidothioate with conventional acylating agents such as acid anhydrides. Acetic acid anhydride is a preferred acylating agent. The acylation reaction is typically carried out at temperatures of from 0.degree. C. to 60.degree. C. in the presence of a catalytic amount of an acid, and in the presence of a solvent. Such solvents include methylene chloride, chloroform, tetrahydrofuran and benzene (see, e.g., U.S. Pat. Nos. 3,716,600 and 3,732,344).
The solvents utilized in the process are suspected carcinogens. Moreover, tetrahydrofuran tends to form dangerous peroxide upon storage. Thus, methylene chloride, chloroform, tetrahydrofuran and benzene are not commercially viable solvents. It would be desirable to develop a process for producing Orthene which does not require the use of a volatile, toxic solvent.